1. Field of the Invention
The present invention relates to image sensor controllers, electronic devices, and methods for controlling image sensors to obtain faster image reading speeds.
2. Description of the Related Art
An image reading device such as an image scanner, facsimile machine or copy machine uses an image sensor, i.e., Charge Coupled Device (CCD), Contact Image Sensor (CIS), or Bucket Brigade Device (BBD), to read images. A particular type of CCD (a CCD line image sensor) is usually employed in an image scanner to read images.
With a line type image sensor, image information is gathered by a light receiving section of the image sensor and supplied in the form of an image data signal to a transfer section of the image sensor. An image sensor controller supplies a transfer clock to the transfer section, and the transfer section uses that transfer clock to successively shift and transfer the image data externally. Then, the outputted analog image data is converted to digital image data, and image processing such as gamma conversion is performed.
However, conventional image sensor controllers use only a fixed transfer clock pattern to drive an image sensor. For this reason, image data for dummy pixel regions, which are essentially unnecessary image data, are transferred at the same transfer rate as image data for effective pixel regions. As a result, the time for shift and transfer operations at the transfer section is unnecessarily long.